1. Field of the Invention
The present invention relates in general to pneumatic therapeutic devices, and in particular to a pneumatic control system for a dynamic pressure wave device.
2. Description of the Prior Art
In the field of medical treatment, it is known that the application of pressure is helpful in the treatment of edema of the extremities as well as in the therapeutic prophylaxis for the prevention of deep vein thrombosis. There are two general types of pneumatic appliance systems known in the prior art for such treatment. One system utilizes a single chamber appliance to provide uniform compression of the extremity. The second system, often referred to as a sequential compression system, utilizes an appliance made up of a series of chambers or segments. In use, a sequential device inflates these appliance chambers one at a time, starting from the end of the appliance surrounding the most distal portion of the extremity until all of the chambers are inflated. Some inflation devices inflate all of the chambers to a uniform pressure while other devices inflate the most distal chamber to the highest pressure and subsequent chambers to a progressively lower pressure, thereby causing a pressure gradient. In all of the above-described devices, a pneumatic control system is electrically or mechanically operated to provide the desired results.
U.S. Pat. No. 2,781,041 discloses an appliance which includes a plurality of cuffs which are inflated in sequence. The inflation and deflation is controlled by a rotary distributor valve which connects each cuff in sequence to a source of compressed air and vents all the cuffs at the same time.
U.S. Pat. No. 3,811,431 discloses an apparatus for providing circulatory assistance to a bed patient to preclude the pooling or clotting of venous blood in the legs or other extremities. A plurality of pairs of pressure cuffs are disposed along the leg of the patient needing circulatory assistance. The cuffs are sequentially inflated through a programming means which can be rotary valve driven by a clock spring motor or fluidic flip flops. A pressure gauge is utilized to control a regulator valve for the compressed air source.
U.S. Pat. No. 3,892,229 discloses an apparatus for alternately applying intermittent compression to the legs of a patient. The control circuit includes a pressure regulating valve for reducing the available inlet supply pressure and an adjustable metering valve for variably controlling the volumetric flow rate of gas to each legging to thereby control the time rate of pressure build-up of each pulse. Respective adjustable pressure relief valves are also provided for variably controlling the maximum pressure permitted in each legging and for relieving the pressure at the end of each pulse. The control circuit includes a timing system for causing the pulses to be delivered at alternate regular intervals to the respective leggings, such timing system comprising a two-diaphragm cycling valve for automatically regulating the alternate charge and discharge of a pair of accumulator tanks, each tank controlling by means of a predetermined rate of pressure increase the timing of the pulses to the respective leggings.
U.S. Pat. No. 4,013,069 discloses a device for applying compressive pressures against a patient's limb from a source of pressurized fluid. The appliance is a sleeve having a plurality of separate fluid pressure chambers progressively arranged longitudinally along the sleeve from the lower portion of the limb to an upper portion of the limb proximal the patient's heart relative to the lower portion. Pneumatic timers are utilized to control the inflation and deflation of the various cuffs.